I am using 2 sources:
Google finance https://finance.google.com/finance/historical?q=INDEXDJX:.DJI
and measuring worth https://measuringworth.com/DJA/
(note: Yahoo finance only goes back to 1985).
For 07/11/1980, Google says the DJIA is 891.13 and Measuring Worth says 887.13
For 07/20/1981, Google says the DJIA is 940.54 and Measuring Worth says 949.54
If anyone has the correct closing amounts or a third link, I’d appreciate that.
Thank you.
For 7/11/1980, advfn.com has a close at 891.13.
For 7/20/1981, advfn.com has a close at 940.54.
I have no idea what advfn.com is or where their data is pulled from.
The link is here:
yearofglad
Thanks for the quick answer AND the link.
(It seems google agreed with advfn.com in both cases.)
Thanks again. 
FYI, I have access to the archives of The New York Times and checking the actual newspaper pages for the day after the dates you mentioned gives the same numbers as Google.
Great - and thanks to you Dewey Finn